1. Field of the Invention
The present invention relates to a fuel feeding device for an engine.
2. Description of the Related Art
Japanese Patent No. 2651974 discloses an engine having a receiver, an injector, and a supply conduit connected therebetween, wherein a mixture of a liquid fuel and an additional fluid in which the additional fluid is in its supercritical state is formed in the receiver, and the mixture is injected from the injector to the engine.
This promotes the atomization of the liquid fuel and therefore provides a good combustion. The reason therefor will be explained, in detail, later.
When, however, the engine is stopped and the temperature in the receiver is lower than the critical temperature of the additional fluid, a separation of the mixture occurs. Finally, layers of the liquid fuel and the additional fluid are formed in the receiver. When the engine is then restarted, the temperature in the receiver cannot exceed the critical temperature of the additional fluid immediately, and therefore the additional fluid cannot be its supercritical state immediately. Accordingly, at this time, the liquid fuel may be injected with the additional fluid which is in the form of a large particle of fluid or gas. In addition, if an outlet of the supplying conduit is connected to the receiver to open out into the additional fluid layer, no fuel may be fed to the engine.
An object of the invention is to provide a fuel feeding device which is capable of preventing the combustion from deteriorating when the additional fluid in the receiver is not in its supercritical state.
According to the present invention, there is provided a fuel feeding device for an engine, comprising: a source of a liquid fuel; a source of an additional fluid; a receiver; mixture forming means for forming in the receiver a mixture of the liquid fuel and the additional fluid fed from the respective sources, the additional fluid in the mixture being in its supercritical state; an injector for injecting the mixture in the receiver to the engine; and a supplying passage for supplying the mixture from the receiver to the injector, the supplying passage having an inlet which opens out in the receiver, wherein the additional fluid has a density different from that of the liquid fuel, which results in, when a separation of the mixture in the receiver is occurred, that layers of the liquid fuel and the additional fluid are formed in the receiver, and wherein the inlet of the supplying passage is positioned with respect to the receiver to open out in the liquid fuel layer.
Note that, in general, a material is considered to be in its supercritical state when the pressure thereof is made higher than its critical pressure and the temperature thereof is made higher than its critical temperature. However, in the present invention, a material is also considered to be in its supercritical state even when the pressure thereof is slightly lower than its critical pressure and the temperature thereof is slightly lower than its critical temperature.